1. Field of the Invention
This invention relates generally to a drain plug for an enclosure and, more particularly, to a drain plug assembly for a battery enclosure that employs a shape memory alloy (SMA) device for actuating the drain plug.
2. Discussion of the Related Art
Electric vehicles are becoming more and more prevalent. These vehicles include hybrid vehicles, such as the extended range electric vehicles (EREV) that combine a battery and a main power source, such as an internal combustion engine, fuel cell systems, etc., and electric only vehicles, such as the battery electric vehicles (BEV). All of these types of electric vehicles employ a high voltage battery that includes a number of battery cells. These batteries can be different battery types, such as lithium ion, nickel metal hydride, lead acid, etc. A typical high voltage battery system for an electric vehicle may include a large number of battery cells or modules including several battery cells to meet the vehicle power and energy requirements.
The high voltage battery on an electric vehicle is typically mounted to a support member and covered with a suitable protective cover that provides a number of functions. For example, the cover is a protective cover in that it prevents the battery cells from being damaged as a result of collision with other objects. Further, the cover provides electrical insulation from the high voltage of the battery to protect individuals and users.
Various sources may cause fluids to accumulate within the battery enclosure. Because the vehicle battery is a high voltage battery, it is desirable to remove or drain any fluids that may have accumulated in the enclosure. In order to provide this drainage, the lower support structure on which the battery pack is mounted typically includes a drain plug that is inserted into an opening in the wall of the enclosure, which can be removed to drain the fluid that accumulates in the enclosure. For example, it is known in the art to provide a flexible plug in a drain hole that is provided at a desirable location in the battery pack enclosure. In one design, the drain hole is about 20 mm in diameter.
Because of the high voltage environment, it is typically necessary that any fluid that has accumulated in the battery enclosure that requires the plug be removed be performed by a trained service technician where the vehicle needs to be taken to a reputable service center. Further, it is sometimes difficult to know if fluid has accumulated in the battery enclosure, requiring such a trip to the service center. Also, the known plugs that are inserted into the drain hole of the battery enclosure often times leak themselves where water from driving through a wet environment may enter the enclosure through the drain hole around the plug.